/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.sql.rowset.spi;

import javax.sql.*;

/**
 * The synchronization mechanism that provides reader/writer capabilities for
 * disconnected <code>RowSet</code> objects.
 * A <code>SyncProvider</code> implementation is a class that extends the
 * <code>SyncProvider</code> abstract class.
 * <P>
 * A <code>SyncProvider</code> implementation is
 * identified by a unique ID, which is its fully qualified class name.
 * This name must be registered with the
 * <code>SyncFactory</code> SPI, thus making the implementation available to
 * all <code>RowSet</code> implementations.
 * The factory mechanism in the reference implementation uses this name to instantiate
 * the implementation, which can then provide a <code>RowSet</code> object with its
 * reader (a <code>javax.sql.RowSetReader</code> object) and its writer (a
 * <code>javax.sql.RowSetWriter</code> object).
 * <P>
 * The Jdbc <code>RowSet</code> Implementations specification provides two
 * reference implementations of the <code>SyncProvider</code> abstract class:
 * <code>RIOptimisticProvider</code> and <code>RIXMLProvider</code>.
 * The <code>RIOptimisticProvider</code> can set any <code>RowSet</code>
 * implementation with a <code>RowSetReader</code> object and a
 * <code>RowSetWriter</code> object.  However, only the <code>RIXMLProvider</code>
 * implementation can set an <code>XmlReader</code> object and an
 * <code>XmlWriter</code> object. A <code>WebRowSet</code> object uses the
 * <code>XmlReader</code> object to read data in XML format to populate itself with that
 * data.  It uses the <code>XmlWriter</code> object to write itself to a stream or
 * <code>java.io.Writer</code> object in XML format.
 *
 * <h3>1.0 Naming Convention for Implementations</h3>
 * As a guide  to naming <code>SyncProvider</code>
 * implementations, the following should be noted:
 * <UL>
 * <li>The name for a <code>SyncProvider</code> implementation
 * is its fully qualified class name.
 * <li>It is recommended that vendors supply a
 * <code>SyncProvider</code> implementation in a package named <code>providers</code>.
 * </UL>
 * <p>
 * For instance, if a vendor named Fred, Inc. offered a
 * <code>SyncProvider</code> implementation, you could have the following:
 * <PRE>
 * Vendor name:  Fred, Inc.
 * Domain name of vendor:  com.fred
 * Package name:  com.fred.providers
 * SyncProvider implementation class name:  HighAvailabilityProvider
 *
 * Fully qualified class name of SyncProvider implementation:
 * com.fred.providers.HighAvailabilityProvider
 * </PRE>
 * <P>
 * The following line of code uses the fully qualified name to register
 * this implementation with the <code>SyncFactory</code> static instance.
 * <PRE>
 * SyncFactory.registerProvider(
 * "com.fred.providers.HighAvailabilityProvider");
 * </PRE>
 * <P>
 * The default <code>SyncProvider</code> object provided with the reference
 * implementation uses the following name:
 * <pre>
 *     com.sun.rowset.providers.RIOptimisticProvider
 * </pre>
 * <p>
 * A vendor can register a <code>SyncProvider</code> implementation class name
 * with Oracle Corporation by sending email to jdbc@sun.com.
 * Oracle will maintain a database listing the
 * available <code>SyncProvider</code> implementations for use with compliant
 * <code>RowSet</code> implementations.  This database will be similar to the
 * one already maintained to list available JDBC drivers.
 * <P>
 * Vendors should refer to the reference implementation synchronization
 * providers for additional guidance on how to implement a new
 * <code>SyncProvider</code> implementation.
 *
 * <h3>2.0 How a <code>RowSet</code> Object Gets Its Provider</h3>
 *
 * A disconnected <code>Rowset</code> object may get access to a
 * <code>SyncProvider</code> object in one of the following two ways:
 * <UL>
 * <LI>Using a constructor<BR>
 * <PRE>
 * CachedRowSet crs = new CachedRowSet(
 * "com.fred.providers.HighAvailabilitySyncProvider");
 * </PRE>
 * <LI>Using the <code>setSyncProvider</code> method
 * <PRE>
 * CachedRowSet crs = new CachedRowSet();
 * crs.setSyncProvider("com.fred.providers.HighAvailabilitySyncProvider");
 * </PRE>
 *
 * </UL>
 * <p>
 * By default, the reference implementations of the <code>RowSet</code> synchronization
 * providers are always available to the Java platform.
 * If no other pluggable synchronization providers have been correctly
 * registered, the <code>SyncFactory</code> will automatically generate
 * an instance of the default <code>SyncProvider</code> reference implementation.
 * Thus, in the preceding code fragment, if no implementation named
 * <code>com.fred.providers.HighAvailabilitySyncProvider</code> has been
 * registered with the <code>SyncFactory</code> instance, <i>crs</i> will be
 * assigned the default provider in the reference implementation, which is
 * <code>com.sun.rowset.providers.RIOptimisticProvider</code>.
 *
 * <h3>3.0 Violations and Synchronization Issues</h3>
 * If an update between a disconnected <code>RowSet</code> object
 * and a data source violates
 * the original query or the underlying data source constraints, this will
 * result in undefined behavior for all disconnected <code>RowSet</code> implementations
 * and their designated <code>SyncProvider</code> implementations.
 * Not defining the behavior when such violations occur offers greater flexibility
 * for a <code>SyncProvider</code>
 * implementation to determine its own best course of action.
 * <p>
 * A <code>SyncProvider</code> implementation
 * may choose to implement a specific handler to
 * handle a subset of query violations.
 * However if an original query violation or a more general data source constraint
 * violation is not handled by the <code>SyncProvider</code> implementation,
 * all <code>SyncProvider</code>
 * objects must throw a <code>SyncProviderException</code>.
 *
 * <h3>4.0 Updatable SQL VIEWs</h3>
 * It is possible for any disconnected or connected <code>RowSet</code> object to be populated
 * from an SQL query that is formulated originally from an SQL <code>VIEW</code>.
 * While in many cases it is possible for an update to be performed to an
 * underlying view, such an update requires additional metadata, which may vary.
 * The <code>SyncProvider</code> class provides two constants to indicate whether
 * an implementation supports updating an SQL <code>VIEW</code>.
 * <ul>
 * <li><code><b>NONUPDATABLE_VIEW_SYNC</b></code> - Indicates that a <code>SyncProvider</code>
 * implementation does not support synchronization with an SQL <code>VIEW</code> as the
 * underlying source of data for the <code>RowSet</code> object.
 * <li><code><b>UPDATABLE_VIEW_SYNC</b></code> - Indicates that a
 * <code>SyncProvider</code> implementation
 * supports synchronization with an SQL <code>VIEW</code> as the underlying source
 * of data.
 * </ul>
 * <P>
 * The default is for a <code>RowSet</code> object not to be updatable if it was
 * populated with data from an SQL <code>VIEW</code>.
 *
 * <h3>5.0 <code>SyncProvider</code> Constants</h3>
 * The <code>SyncProvider</code> class provides three sets of constants that
 * are used as return values or parameters for <code>SyncProvider</code> methods.
 * <code>SyncProvider</code> objects may be implemented to perform synchronization
 * between a <code>RowSet</code> object and its underlying data source with varying
 * degrees of of care. The first group of constants indicate how synchronization
 * is handled. For example, <code>GRADE_NONE</code> indicates that a
 * <code>SyncProvider</code> object will not take any care to see what data is
 * valid and will simply write the <code>RowSet</code> data to the data source.
 * <code>GRADE_MODIFIED_AT_COMMIT</code> indicates that the provider will check
 * only modified data for validity.  Other grades check all data for validity
 * or set locks when data is modified or loaded.
 * <OL>
 * <LI>Constants to indicate the synchronization grade of a
 * <code>SyncProvider</code> object
 * <UL>
 * <LI>SyncProvider.GRADE_NONE
 * <LI>SyncProvider.GRADE_MODIFIED_AT_COMMIT
 * <LI>SyncProvider.GRADE_CHECK_ALL_AT_COMMIT
 * <LI>SyncProvider.GRADE_LOCK_WHEN_MODIFIED
 * <LI>SyncProvider.GRADE_LOCK_WHEN_LOADED
 * </UL>
 * <LI>Constants to indicate what locks are set on the data source
 * <UL>
 * <LI>SyncProvider.DATASOURCE_NO_LOCK
 * <LI>SyncProvider.DATASOURCE_ROW_LOCK
 * <LI>SyncProvider.DATASOURCE_TABLE_LOCK
 * <LI>SyncProvider.DATASOURCE_DB_LOCK
 * </UL>
 * <LI>Constants to indicate whether a <code>SyncProvider</code> object can
 * perform updates to an SQL <code>VIEW</code> <BR>
 * These constants are explained in the preceding section (4.0).
 * <UL>
 * <LI>SyncProvider.UPDATABLE_VIEW_SYNC
 * <LI>SyncProvider.NONUPDATABLE_VIEW_SYNC
 * </UL>
 * </OL>
 *
 * @author Jonathan Bruce
 * @see javax.sql.rowset.spi.SyncFactory
 * @see javax.sql.rowset.spi.SyncFactoryException
 */
public abstract class SyncProvider {

  /**
   * Creates a default <code>SyncProvider</code> object.
   */
  public SyncProvider() {
  }

  /**
   * Returns the unique identifier for this <code>SyncProvider</code> object.
   *
   * @return a <code>String</code> object with the fully qualified class name of this
   * <code>SyncProvider</code> object
   */
  public abstract String getProviderID();

  /**
   * Returns a <code>javax.sql.RowSetReader</code> object, which can be used to
   * populate a <code>RowSet</code> object with data.
   *
   * @return a <code>javax.sql.RowSetReader</code> object
   */
  public abstract RowSetReader getRowSetReader();

  /**
   * Returns a <code>javax.sql.RowSetWriter</code> object, which can be
   * used to write a <code>RowSet</code> object's data back to the
   * underlying data source.
   *
   * @return a <code>javax.sql.RowSetWriter</code> object
   */
  public abstract RowSetWriter getRowSetWriter();

  /**
   * Returns a constant indicating the
   * grade of synchronization a <code>RowSet</code> object can expect from
   * this <code>SyncProvider</code> object.
   *
   * @return an int that is one of the following constants: SyncProvider.GRADE_NONE,
   * SyncProvider.GRADE_CHECK_MODIFIED_AT_COMMIT, SyncProvider.GRADE_CHECK_ALL_AT_COMMIT,
   * SyncProvider.GRADE_LOCK_WHEN_MODIFIED, SyncProvider.GRADE_LOCK_WHEN_LOADED
   */
  public abstract int getProviderGrade();


  /**
   * Sets a lock on the underlying data source at the level indicated by
   * <i>datasource_lock</i>. This should cause the
   * <code>SyncProvider</code> to adjust its behavior by increasing or
   * decreasing the level of optimism it provides for a successful
   * synchronization.
   *
   * @param datasource_lock one of the following constants indicating the severity level of data
   * source lock required:
   * <pre>
   *           SyncProvider.DATASOURCE_NO_LOCK,
   *           SyncProvider.DATASOURCE_ROW_LOCK,
   *           SyncProvider.DATASOURCE_TABLE_LOCK,
   *           SyncProvider.DATASOURCE_DB_LOCK,
   * </pre>
   * @throws SyncProviderException if an unsupported data source locking level is set.
   * @see #getDataSourceLock
   */
  public abstract void setDataSourceLock(int datasource_lock)
      throws SyncProviderException;

  /**
   * Returns the current data source lock severity level active in this
   * <code>SyncProvider</code> implementation.
   *
   * @return a constant indicating the current level of data source lock active in this
   * <code>SyncProvider</code> object; one of the following:
   * <pre>
   *           SyncProvider.DATASOURCE_NO_LOCK,
   *           SyncProvider.DATASOURCE_ROW_LOCK,
   *           SyncProvider.DATASOURCE_TABLE_LOCK,
   *           SyncProvider.DATASOURCE_DB_LOCK
   * </pre>
   * @throws SyncProviderException if an error occurs determining the data source locking level.
   * @see #setDataSourceLock
   */
  public abstract int getDataSourceLock()
      throws SyncProviderException;

  /**
   * Returns whether this <code>SyncProvider</code> implementation
   * can perform synchronization between a <code>RowSet</code> object
   * and the SQL <code>VIEW</code> in the data source from which
   * the <code>RowSet</code> object got its data.
   *
   * @return an <code>int</code> saying whether this <code>SyncProvider</code> object supports
   * updating an SQL <code>VIEW</code>; one of the following: SyncProvider.UPDATABLE_VIEW_SYNC,
   * SyncProvider.NONUPDATABLE_VIEW_SYNC
   */
  public abstract int supportsUpdatableView();

  /**
   * Returns the release version of this <code>SyncProvider</code> instance.
   *
   * @return a <code>String</code> detailing the release version of the <code>SyncProvider</code>
   * implementation
   */
  public abstract String getVersion();

  /**
   * Returns the vendor name of this <code>SyncProvider</code> instance
   *
   * @return a <code>String</code> detailing the vendor name of this <code>SyncProvider</code>
   * implementation
   */
  public abstract String getVendor();

    /*
     * Standard description of synchronization grades that a SyncProvider
     * could provide.
     */

  /**
   * Indicates that no synchronization with the originating data source is
   * provided. A <code>SyncProvider</code>
   * implementation returning this grade will simply attempt to write
   * updates in the <code>RowSet</code> object to the underlying data
   * source without checking the validity of any data.
   */
  public static final int GRADE_NONE = 1;

  /**
   * Indicates a low level optimistic synchronization grade with
   * respect to the originating data source.
   *
   * A <code>SyncProvider</code> implementation
   * returning this grade will check only rows that have changed.
   */
  public static final int GRADE_CHECK_MODIFIED_AT_COMMIT = 2;

  /**
   * Indicates a high level optimistic synchronization grade with
   * respect to the originating data source.
   *
   * A <code>SyncProvider</code> implementation
   * returning this grade will check all rows, including rows that have not
   * changed.
   */
  public static final int GRADE_CHECK_ALL_AT_COMMIT = 3;

  /**
   * Indicates a pessimistic synchronization grade with
   * respect to the originating data source.
   *
   * A <code>SyncProvider</code>
   * implementation returning this grade will lock the row in the originating
   * data source.
   */
  public static final int GRADE_LOCK_WHEN_MODIFIED = 4;

  /**
   * Indicates the most pessimistic synchronization grade with
   * respect to the originating
   * data source. A <code>SyncProvider</code>
   * implementation returning this grade will lock the entire view and/or
   * table affected by the original statement used to populate a
   * <code>RowSet</code> object.
   */
  public static final int GRADE_LOCK_WHEN_LOADED = 5;

  /**
   * Indicates that no locks remain on the originating data source. This is the default
   * lock setting for all <code>SyncProvider</code> implementations unless
   * otherwise directed by a <code>RowSet</code> object.
   */
  public static final int DATASOURCE_NO_LOCK = 1;

  /**
   * Indicates that a lock is placed on the rows that are touched by the original
   * SQL statement used to populate the <code>RowSet</code> object
   * that is using this <code>SyncProvider</code> object.
   */
  public static final int DATASOURCE_ROW_LOCK = 2;

  /**
   * Indicates that a lock is placed on all tables that are touched by the original
   * SQL statement used to populate the <code>RowSet</code> object
   * that is using this <code>SyncProvider</code> object.
   */
  public static final int DATASOURCE_TABLE_LOCK = 3;

  /**
   * Indicates that a lock is placed on the entire data source that is the source of
   * data for the <code>RowSet</code> object
   * that is using this <code>SyncProvider</code> object.
   */
  public static final int DATASOURCE_DB_LOCK = 4;

  /**
   * Indicates that a <code>SyncProvider</code> implementation
   * supports synchronization between a <code>RowSet</code> object and
   * the SQL <code>VIEW</code> used to populate it.
   */
  public static final int UPDATABLE_VIEW_SYNC = 5;

  /**
   * Indicates that a <code>SyncProvider</code> implementation
   * does <B>not</B> support synchronization between a <code>RowSet</code>
   * object and the SQL <code>VIEW</code> used to populate it.
   */
  public static final int NONUPDATABLE_VIEW_SYNC = 6;
}
